JP2990378B2 - Ink composition for inkjet printer - Google Patents

Abstract

An ink jet printer ink of the kind comprising a dispersion of a pigment in a non-aqueous diluent wherein the diluent is a single phase liquid comprising a major amount of aliphatic hydrocarbon and a minor amount of a polar component, comprising oleyl alcohol alone or in combination with a least one other polar liquid such as an ether or an ester.

Description

Description: TECHNICAL FIELD The present invention relates to ink compositions used in ink jet printers, and more particularly to such compositions comprising a dispersion of a pigment in a non-aqueous diluent.

BACKGROUND OF THE INVENTION Ink jet printers of the type in which drops of ink are pressed under pressure through very small nozzles in a print head are of increasing interest in both office and general industrial use. In one type of printer, known as a "continuous" printer, droplets of ink that are produced continuously are charged individually in response to a signal and directed to a substrate to be printed. Pass through the charge region. The droplets pass through the electric field and are deflected by an amount that depends on the charge and the strength of the electric field. Droplets that are not required to form a print on the substrate are directed to the channel of the bypass. The inks used in these printers need to be conductive. In other types of printers, known as "drop-on-demand" (DOD) printers, droplets of ink are ejected from printhead nozzles only when required during the printing process. Drop-on-demand printers can use a series of droplets ejected by electrically accelerated inkjet or pressure impulse bombardment. In the latter type of DOD printer, each drop of ink is
For example, the nozzles are fired individually by pressure pulses induced by the use of piezoelectric actuators acting on the ink in the channels supplied to the nozzles, or by the generation of bubbles in response to heat pulses. Ink used in this type of printer, need not be electrically conductive, preferably non-ionic, and such as at least 10 of the very low conductivity so as to have a resistance of ⁶ ohm cm Things.

In parallel with the development of these printers, special inks suitable for use in them have been developed.

These inks are required to meet multiple criteria. For example, they do not degrade, especially without noticeable settling or solidification of pigment particles under normal climatic conditions.
Must be able to store. They must also be sufficiently liquid at normal printer operating temperatures (typically 10-40 ° C.) to be ejected from the printhead nozzles using moderate pressure. They must not degrade during periods of inactivity in the printhead during normal operation, e.g., due to diluent evaporation, phase separation, solidification or detrimental effects of air or moisture, and they may then become abnormal. Do not wet the zone of the printhead surrounding the nozzle orifice to the extent that it will lead to a large volume of printhead bleed that will direct operation. To ensure that printhead wetting does not occur to an unacceptable degree, the ink should be at least 100 μm.s when measured on a surface with a surface energy of 10 ± ¹ mN.m ^-1 .
It has been found desirable to have a dewetting rate of ^-1 . Surface energy, Adamson, 1976
AW 3rd `` Physical Chemistry of Surfaces '' Jo
Zisman written on page 351ff of hn Wiley & Sons
Is measured as the critical surface tension from the static contact angle of a pure liquid using the method of Examples of these surfaces are 1994
No. 9417445.5, filed Aug. 30, 2014. For a discussion of the dewetting rate and its measurement, reference is made to a paper by Redon et al. In Physical Review Letters. 66, No. 6, February 11, 1991, pp. 715-718. Preferably, the dewetting rate of the ink, when measured as defined above, is at least 200, more preferably at least 300 and more preferably at least 1000 μm.sec- ¹ .

Other properties of the ink found to be by weight are preferably about 22-36 mN.m ^-1 at 25 ° C., and more preferably
Its surface tension, which must be in the range of 24-32 mN.m- ¹ .

Because inks must also provide good definition prints, and coated papers are expensive, ink jet printer inks have good color density on plain paper, i.e., uncoated paper. It must be possible to produce sufficiently sharp prints.

Good print clarity quality includes, among other things, (a) rapid formation of solid colored dots from the ink composition,
(B) the concentration of the ink colorant on the surface of the paper; (c) the control of the spread of the color dots formed on the surface of the paper substrate from the ink droplets; (d) one dot of a different color from the next. Requires limited bleeding of one color ink into a single dot and uniformity of color and color density in areas of solid dots formed from droplets. Preferably, also the printing should not degrade as a result of the action of water or light.

Many of the above criteria govern conflicting properties of the ink. For example, a decrease in viscosity increases fluidity, which increases the risk of ink droplet spreading on the surface of the paper before the ink dries. Similarly, the danger of drying the ink in the nozzle is reduced by reducing the volatility of the diluent, but the opposite is required to help the rapid drying of the ink droplets on the substrate. Would. Optimizing these properties is therefore a compromise. Moreover, changing the composition of the ink in an attempt to obtain an optimization of these properties is often
It has been found to adversely affect other desirable properties.

Therefore, there is a continuing trend towards the formation of images, especially with smaller nozzles and higher resolutions, but with it, there is always a need for research for improved inks.

DISCLOSURE OF THE INVENTION The present inventor has found that the above criteria are met or very close to them, and that the nozzle diameter is 50 hours.
Inks have been developed that can be used with printheads of μm or less, for example 20 μm or less, to always produce excellent quality prints.

According to the present invention, there is provided an ink-jet printer ink comprising a pigment dispersed in a non-aqueous diluent, wherein the diluent is a single-phase liquid containing an aliphatic hydrocarbon and a polar component, Hydrogen forms the major amount of the diluent by weight, and the polar component is oleyl alcohol alone or in combination with at least one other polar liquid, the total amount of which is 5-45% by weight of the diluent. % Is provided.

The aliphatic hydrocarbon component of the ink comprises greater than 50% by weight of the diluent, and preferably greater than 50% by weight of the ink composition, and comprises a single component or mixture;
Further, it may be a distillate from the fractionation of a natural or synthetic hydrocarbon mixture, for example as sold under the trade name EXXSOL. Generally, it will have a boiling point of at least 100 ° C and preferably at least 200 ° C. If it is a mixture, boiling point is to be understood as meaning the temperature at which the mixture starts to boil.

The diluent must be essentially hydrocarbon in nature, but the presence of polar components, including small amounts of oleyl alcohol, is essential. Alcohols can be used alone or with one or more other polar liquids, such as esters, ethers, amides or other alcohols. Ethers are preferred, and examples include the monoalkyl ethers of ethylene and propylene glycol and polyglycols, such as ethylene glycol monobutyl ether, dipropylene glycol monomethyl ether and tripropylene glycol monomethyl ether. The nature and quality of the other polar liquids is such that the boiling point of the diluent is at least 10
It will be appreciated that it should be such that it is 0 ° C, preferably at least 200 ° C. On the other hand, ink
All must remain fluid at similar operating temperatures, so it is desirable that the freezing point or temperature at which the solid first begins to form is below 10 ° C, preferably below 7 ° C.

The amount of oleyl alcohol or the mixture of oleyl alcohol and other polar liquids present in the diluent may be greater than 0.1 MPa ^1/2 , as otherwise problems with wetting of the zone surrounding the orifice may occur. It must be such as to provide a diluent with a polar solubility parameter. On the other hand, this parameter should preferably be less than or equal to 5 MPa ^1/2, as it may not be possible to introduce that it could otherwise be present with other materials in the printing system. Preferably, this parameter is
It will be in the range of 0.2-2 MPa ^1/2 . In this specification regarding the polar solubility parameter, Patton.TC "Paint
Flow & Pigment Dispersion "Second Edition, Wiley In
Hansen, further detailed by terscience, 1979.
CM and Skaarup, K. Journal of Paint Technolog
y, 39 No. 51, pp. 511-514 (1967). It is also important that the total amount of polar liquid used is such that the resulting mixture with hydrocarbons is a single phase.

Thus, the amount of oleyl alcohol contained in the ink depends on whether it is the sole polar liquid component, or whether it is used in a mixture with other polar liquids, and, if so, on these liquids. And the degree of polarity. Generally, when it is the sole polar component, it is 5-40% of the total weight of the diluent, more preferably 10-10%.
Used at -40%, and if it is used with other polar liquids, it will be used in amounts ranging from 5-30% by weight. The total amount of polar liquid is generally 5 to 45% by weight of the diluent, preferably 5 to 40% by weight, more preferably 10 to 40% by weight.
In the range.

As mentioned above, the diluent must be non-aqueous,
That is, it must contain no more than 5% by weight of water. At any time, the amount of water present, if any, must not be such as to cause the formation of a second liquid phase.

Any suitable pigment can be used if it forms a stable dispersion in the chosen diluent.
Preferred pigments are found among those characterized in the Color Index as pigment dyes. Preferably, the pigment will be of a primary substractive hue. The pigment must be lightfast and thermally stable over repeated warming. The pigment must be water-insoluble once applied to the substrate to prevent contamination on contact with water-containing substances. Carbon black can also be used.

The particle size of the pigment is suitably 1.5 μm or less and preferably 1.0 μm or less, more preferably 0.5 μm or less, even more preferably 0.3 μm or less.

It is also preferred that the specific gravity of the pigment be close to that of the selected solvent, as this will reduce the likelihood of settling on standing.

The appropriate concentration of the pigment will depend on its properties,
Generally, it will be in the range of 2-20% by weight of the ink, more usually 4-5%.

Generally, it will be necessary to include a dispersant to effectively disperse the pigment particles in the diluent and to stabilize the dispersion. Preferably, the dispersant is a solution in a diluent,
That is, it will be dissolved in a diluent or solvated so that the mixture of diluent and dispersant is indistinguishable from a true solution.

The dispersant must be able to stabilize the dispersion of the selected pigment in the required concentration in the selected solvent and maintain the dispersion during storage and under the operating conditions encountered by the printhead. Polymeric dispersants are generally preferred for their efficiency. Examples of suitable dispersants are
Polyesteramine dispersants, such as Z with the trade name SOLSPERSE
those sold by eneca Colors, and especially those described in British Patent A 2001083, ie free carboxylic acids in which there are at least two polyester chains attached to each poly (lower alkylene) imine chain It includes a reaction product of a polyester having a group and a poly (lower alkylene) imine. Examples of other dispersants which can be used are those marketed under the trade names EFKA and DISPERBYK. Mixtures of dispersants can be used if desired.

For a given combination of diluent, dispersant and pigment, the appropriate amount of dispersant can be readily determined by experiment. In general, it has been found that as the concentration of the dispersant increases from zero, the viscosity of the mixture decreases to a minimum and then begins to increase again. The theoretical optimum amount of dispersant is that which gives the lowest viscosity for the mixture so that it provides the most effective dispersion of the pigment. Generally, a suitable amount of dispersant is
100-200% of the optimal amount, more preferably 110-150%
You can see that it is in the range. Higher amounts can be used, but in general, the amount of dispersant will be about 10-100% by weight of the amount of pigment used.

The energy required to eject a droplet of ink is, in particular, a function of the viscosity, and for this and other reasons, it is preferred that the viscosity of the ink be less than or equal to 60 mPa.s. The viscosity is mainly determined by the viscosity of the diluent and the nature and concentration of the dispersant, but also the nature and concentration of the pigment. The most preferred range of viscosity is Bohlin
6-30 mP measured at 30 ° C using CS Viscometer
as. The invention is illustrated by the following examples in which all parts are by weight.

EXAMPLES Example 1 The ink has a boiling range of 280-317 ° C and EXXON
65.05 parts of a mixture of aliphatic hydrocarbons marketed as EXXSOL D140, 20 parts of oleyl alcohol marketed by Croda as NOVOL, 40% solution of polyesteramine hyperdispersant in aliphatic hydrocarbons (SOLSPERSE
13940) 3.75 parts, substituted ammonium phthalocyanine sulfonate (SOLSPERSE 5000) 0.2 parts and REGAL Black
Made from 11 parts. SOLSPERSE 13940 and SOLSPERSE5
000 are both marketed by Zeneca Colors.
SOLSPERSE is a trademark required by Zeneca Limited.

 The properties of the ink were as follows.

(1) Measured at 30 ° C. using a Bohlin CS rheometer having a CP4 / 40 measurement system.

(2) Measured as described on a fluorosilane surface with a surface energy of 10 ± ¹ mN.m ⁻¹ .

(3) Kruess K12 Processor Tensiometer S at 20 ° C
Measured using ystem.

The ink was stable on storage, could be used for printing continuously for a considerable period of time without blockage or malfunction, and gave excellent definition prints.

Example 2-5 A series of experiments demonstrate the effect on stability (NOVOL and EXXSOL D14) by changing the concentration of NOVOL in the ink of Example 1.
(The total amount of 0 remained unchanged).

Stability was evaluated by measuring the wavelength dependence of turbidity of the ink. Over a wide range of turbidity spectra, turbidity τ is related to wavelength λ by τ = k / λ ^exp . The value of exp is obtained by the following method. The ink is 1: 5000 in a liquid blend equal to the ink diluent
And the optical density (OD) is between 400-900 nm
Measured on a Cary I UV-Visible spectrophotometer using a 1 cm path length cuvette, exp is lo to log ₁₀ (λ).
Obtained as the slope from a linear regression of g ₁₀ (OD). To assess stability, samples of the ink were stored at 65 ° C. and room temperature, and turbidity measurements were taken periodically for 12 weeks. Ink, if the value of exp decreases by 15 in 12 weeks
%, It can be considered stable. The results are as follows.

* Comparative Example Example 6 The ink of Example 1 was modified by reducing the amount of EXXSOL D140 and NOVOL to 57.30 parts and 71.75 parts, respectively, and including 10 parts of tripropylene glycol monomethyl ether. The resulting composition has a boiling and freezing point similar to that of Example 1, a polar solubility parameter of 1.07 MPa ^0.5 , a viscosity of 9 mPa.s, a surface tension of 24.9 mN.m ^-1 and 1.6 m
It had a dewetting rate of msec- ¹ . Its performance was similar to that of the ink of Example 1.

Example 7 An ink was manufactured with the following composition.

REGAL Black 250R 11% SOLSPERSE 13940 3.75% SOLSPERSE 5000 0.2% COASOL 20% NOVOL 17.5% EXXSOL D140 47.55% COASOL is a mixture of dibutyl esters of succinic, glutaric and adipic acids. The ink had a viscosity of 10 mPa.s, a polar solubility parameter of 1.1 MPa ^0.5 , and properties very similar to the ink of Example 6.

The following are examples of inks according to the present invention using pigments other than black.

Example 8 PALIOTOL Yellow D1115 5% SOLSPERSE 13940 3.75% NOVOL 24% EXXSOL D140 67.25% Example 9 MONASTRAL Blue FGX 5% SOLSPERSE 13940 5% SOLSPERSE 5000 0.5% NOVOL 15% EXXSOL D140 74.5% Example 10 HOSTAPERM Red E5B02% SOLSPERSE 13940 8% NOVOL 9% EXXSOL D140 74% The ink of Example 8-9 has a viscosity of 10 ± 0.5 mPa.s, and
It had a dewetting rate in the range of 1.2-2.7 mm.sec- ¹ . They were all stable on storage, could be used to print continuously for a considerable period of time without blockage or malfunction, and gave excellent definition prints.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Woods, Jill Cambridgeshire, UK 159 9HS March Kingfisher Cross 11 (58) Field surveyed (Int. Cl. ⁶ , DB name) C09D 11/00- 11/14

Claims (15)

(57) [Claims] 1. An ink jet printer ink comprising a pigment dispersed in a non-aqueous diluent, wherein the diluent is a single phase liquid containing an aliphatic hydrocarbon and a polar component,
The aliphatic hydrocarbons form a major amount of the diluent by weight;
The polar component is oleyl alcohol alone or a combination thereof with at least one other polar liquid, and the total amount forms 5 to 45% by weight of the diluent. 2. The ink for an ink jet printer according to claim 1, further comprising a dispersant. 3. The ink according to claim 1, wherein the dispersant is a polyesteramine. 4. The dispersant is a reaction product of a poly (lower alkylene) imine and a polyester having a free carboxylic acid group, and the reaction product is bonded to each poly (lower alkylene) imine chain. 3. The ink for an ink jet printer according to claim 2, wherein at least two polyester chains are present. 5. The polar component of the diluent is oleyl alcohol,
The ink for an inkjet printer according to claim 1, further comprising at least one of an ester and an ether. 6. The ink for an ink jet printer according to claim 1, wherein the polar component forms 5 to 40% by weight of the diluent. 7. The ink according to claim 1, wherein the polar component forms 10 to 40% by weight of the diluent. 8. The ink according to claim 1, wherein the pigment is present in an amount of 4 to 15% by weight of the ink. 9. An amount of the dispersant which gives the ink a minimum viscosity of 11
The ink for an ink jet printer according to any one of claims 1 to 8, which is present in an amount of 0 to 150%. 10. The method of claim 1 having a boiling point of at least 200 ° C.
9. The ink for an ink jet printer according to any one of items 1 to 8. 11. The ink for an ink jet printer according to claim 1, which has a freezing point of 7 ° C. or lower. 12. The ink for an ink jet printer according to claim 1, having a polar solubility parameter in the range of 0.2 to ² MPa ^1/2 . 13. When measured on a surface having a surface energy of 10 ± 1mN.m ^-1, inkjet printer of any one of claims 1 to 12 having a dewetting velocity of at least 200 [mu] m. Sec ^-1 For ink. 14. An ink-jet according to claim 1, having a viscosity in the range from 6 to 30 mPa.s, measured at 30 ° C. using a Bohlin CS rheometer with a CP4 / 40 measuring system. Printer ink. 15. The ink for an ink jet printer according to claim 1, which has a surface tension at 25 ° C. in the range of 24 to 32 mN.m ⁻¹ .